There are many different techniques used to achieve the desired separation of contaminants from air and other fluid streams. When the contaminant concentration is not large in comparison to the bulk stream, two techniques, adsorption and absorption are generally effective. On occasion, additional components are added to adsorbents to enhance the benefits of physical adsorption by utilizing chemisorption. However, utilizing either an absorbent agent or an adsorbent agent with added chemisorption components results in a purification system that is not readily regenerable, whereas utilizing physical adsorption alone allows for the regeneration of the adsorption agents, in general, either by pressure or temperature variation techniques. The weight and complexity of many regeneration systems, in general, limits their feasibility for use in mobile applications.
One area where adequate purification of a fluid stream has life and death consequences is in the defense against chemical warfare agents. In the past, specially treated activated charcoal adsorption medium have been developed capable of adsorbing a broad spectrum of chemical warfare agents ranging from low molecular weight agents such as hydrogen cyanide and cyanogen chloride to high molecular weight (nerve agents) agents such as soman and sarin and very large agents such as "BZ" and "VX".
The present state-of-the-art for Chemical Defense Collective Protection for enclosures, armored vehicles and the like utilizes such specially treated activated charcoal adsorption medium in filters and the like devices, but they have been found to exhibit many drawbacks. The filters have limited shelf life, are readily fouled by a variety of nontoxic contaminants such as water and various hydrocarbon vapors, require frequent replacement and they cannot be regenerated, necessitating replacement, typically, while the protective system is shut down.